Generally, various thin-film forming techniques are used to fabricate semiconductor devices or flat panel display devices. One of them is a vacuum thermal evaporation method. The vacuum thermal evaporation method is a method of forming a thin film by placing a substrate at an upper side within a vacuum container, and heating an evaporator, which is placed below the substrate and contains a material to be evaporated, so that the evaporated material can be deposited on the substrate.
FIG. 1 shows a point evaporator that is most popularly used in the vacuum thermal evaporation method. As shown in FIG. 1, the point evaporator 21 includes a cylindrical container with a spouting portion. A material to be evaporated is filled into the cylindrical container that in turn is heated to evaporate the material, so that the evaporated material spouts from the container toward a substrate to form a thin film. However, since the point evaporator causes most of the evaporated material to spout therefrom in a direction 22 directed by the spouting portion, it has a problem in that a large-area uniform thin film cannot be obtained. In order to solve this problem, as shown in FIG. 1, an evaporation method in which the point evaporator is placed at a peripheral region of the substrate 1 and the substrate is rotated has been used. However, this evaporation method has further problems in that the addition of an apparatus for rotating the substrate makes the evaporation system complicated and causes defects in final products, and the efficiency of use of a material is lowered.
Moreover, since the spouting portion is located at a center that is far away from a lateral heated portion in the conventional point evaporator, there is a disadvantage in that the evaporated material may be easily condensed at the spouting portion.
In order to solve these problems in the conventional point evaporator, the present inventor proposed a conical-nozzle evaporator. In case of the conical nozzle, it is difficult to achieve a desired spouting distribution, to process the nozzle and to grind the inside of the nozzle. Furthermore, since an evaporation tube is located at the center of the nozzle, there is a disadvantage in that an evaporated material is condensed inside the evaporation tube in the same manner as the conventional point evaporator.